Method for producing R-Fe-B-based, sintered magnet

Abstract

An R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, is produced by the method including the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less to prepare a mixture; charging the mixture under pressure into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing a mineral oil and/or a synthetic oil from the mixture; compressing the mixture in the die cavity to carry out a wet molding while orientating the powder to prepare a green body; heating the green body to a temperature up to 500° C. at a speed of 10° C./min or less under pressure of 10 -1 Torr or less for 30 minutes or more to remove a mineral oil and/or a synthetic oil from the green body; and then sintering the green body.

What is claimed is: 
     
       1. A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of: mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil to prepare a mixture, wherein the mineral oil and the synthetic oil, used alone or in combination, have a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less at room temperature;   charging said mixture into a die cavity under pressure so as to have a filling density of 1.8 g/cm 3  or more;   subjecting said mixture to a wet molding to prepare a green body; and then   sintering said green body.   
     
     
       2. A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of: mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil to prepare a mixture, wherein the mineral oil and the synthetic oil, used alone or in combination, have a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less at room temperature;   charging said mixture into a die cavity under pressure so as to have a filling density of 1.8 g/cm 3  or more while applying an oriented magnetic field to said die cavity;   subjecting said mixture to a wet molding while orienting said powder to prepare a green body; and then   sintering said green body.   
     
     
       3. A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of: finely pulverizing an R-Fe-B-based magnet material in an inert gas atmosphere to prepare fine R-Fe-B-based magnet powder in a dry state;   introducing said fine R-Fe-B-based magnet powder into a mineral oil and/or a synthetic oil in an inert gas atmosphere to prepare a mixture, wherein the mineral oil and the synthetic oil, used alone or in combination, have a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less at room temperature;   charging said mixture into a die cavity under pressure so as to have a filling density of 1.8 g/cm 3  or more while applying an oriented magnetic field to said die cavity;   subjecting said mixture to a wet molding while orienting said powder to prepare a green body; and then   sintering said green body.   
     
     
       4. The method for producing an R-Fe-B-based, sintered magnet according to claim 1, wherein said mixture is charged into said die cavity under pressure of 1 kgf/cm 2  or more. 
     
     
       5. The method for producing an R-Fe-B-based, sintered magnet according to claim 2, wherein said mixture is charged into said die cavity to which an orientated magnetic field of 2 kOe or more is applied, and said mixture is subjected to a wet molding while orientating said powder in said die cavity. 
     
     
       6. The method for producing an R-Fe-B-based, sintered magnet according to claim 1, wherein the amount of said fine R-Fe-B-based magnet powder is 50-80 weight % based on the mixture of said fine R-Fe-B-based magnet powder with said mineral oil or said synthetic oil. 
     
     
       7. The method for producing an R-Fe-B-based, sintered magnet according to claim 2, wherein the amount of said fine R-Fe-B-based magnet powder is 50-80 weight % based on the mixture of said fine R-Fe-B-based magnet powder with said mineral oil or said synthetic oil. 
     
     
       8. The method for producing an R-Fe-B-based, sintered magnet according to claim 3, wherein the amount of said fine R-Fe-B-based magnet powder is 50-80 weight % based on the mixture of said fine R-Fe-B-based magnet powder with said mineral oil or said synthetic oil. 
     
     
       9. The method for producing an R-Fe-B-based, sintered magnet according to claim 1, wherein the green body is kept wet with a mineral oil, a synthetic oil or a hydrophobic organic solvent until said green body is sintered. 
     
     
       10. The method for producing an R-Fe-B-based, sintered magnet according to claim 2, wherein the green body is kept wet with a mineral oil, a synthetic oil or a hydrophobic organic solvent until said green body is sintered. 
     
     
       11. The method for producing an R-Fe-B-based, sintered magnet according to claim 3, wherein the green body is kept wet with a mineral oil, a synthetic oil or a hydrophobic organic solvent until said green body is sintered. 
     
     
       12. The method for producing an R-Fe-B-based, sintered magnet according to claim 1, wherein the green body is kept at a temperature of 50°-500° C. under pressure of 10 -1  Torr or less for 30 minutes or more to remove said mineral oil or said synthetic oil, and then sintered. 
     
     
       13. The method for producing an R-Fe-B-based, sintered magnet according to claim 2, wherein the green body is kept at a temperature of 50°-500° C. under pressure of 10 -1  Torr or less for 30 minutes or more to remove said mineral oil or said synthetic oil, and then sintered. 
     
     
       14. The method for producing an R-Fe-B-based, sintered magnet according to claim-3, wherein the green body is kept at a temperature of 50°-500° C. under pressure of 10 -1  Torr or less for 30 minutes or more to remove said mineral oil or said synthetic oil, and then sintered. 
     
     
       15. The method for producing an R-Fe-B-based, sintered magnet according to claim 1, wherein the green body is heated from room temperature to a temperature up to 500° C. at a temperature-elevating speed of 10° C./min or less under pressure of 10 -1  Torr or less to remove said mineral oil or said synthetic oil, and then sintered. 
     
     
       16. The method for producing an R-Fe-B-based, sintered magnet according to claim 2, wherein the green body is heated from room temperature to a temperature up to 500° C. at a temperature-elevating speed of 10° C./min or less under pressure of 10 -1  Torr or less to remove said mineral oil or said synthetic oil, and then sintered. 
     
     
       17. The method for producing an R-Fe-B-based, sintered magnet according to claim 3, wherein the green body is heated from room temperature to a temperature up to 500° C. at a temperature-elevating speed of 10° C./min or less under pressure of 10 -1  Torr or less to remove said mineral oil or said synthetic oil, and then sintered. 
     
     
       18. A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less to prepare a mixture; charging said mixture under pressure so as to have a filling density of 1.8 g/cm 3  or more into a die cavity equipped with a filter while removing said mineral oil and/or said synthetic oil from said mixture; compressing said mixture in said die cavity to carry out a wet molding for preparing a green body; heating said green body to a temperature up to 500° C. at a temperature-elevating speed of 10° C./min or less under pressure of 10 -1  Torr or less for 30 minutes or more to remove said mineral oil and/or said synthetic oil from said green body; and then sintering said green body. 
     
     
       19. A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less to prepare a mixture; charging said mixture under pressure so as to have a filling density of 1.8 g/cm 3  or more into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing said mineral oil and/or said synthetic oil from said mixture; compressing said mixture in said die cavity to carry out a wet molding while orientating said powder to prepare a green body; heating said green body to a temperature up to 500° C. at a temperature-elevating speed of 10° C./min or less under pressure of 10 -1  Torr or less for 30 minutes or more to remove said mineral oil and/or said synthetic oil from said green body; and then sintering said green body. 
     
     
       20. A method for producing as R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of finely pulverizing an R-Fe-B-based magnet material in an inert gas atmosphere to prepare fine R-Fe-B-based magnet powder in a dry state; introducing said fine R-Fe-B-based magnet powder in an inert gas atmosphere into a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150°-400° C. and a kinetic viscosity of 10 cSt or less; mixing said fine R-Fe-B-based magnet powder with said mineral oil and/or said synthetic oil to prepare a mixture; charging said mixture under pressure so as to have a filling density of 1.8 g/cm 3  or more into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing said mineral oil and/or said synthetic oil from said mixture; compressing said mixture in said die cavity to carry out a wet molding while orientating said powder to prepare a green body; heating said green body to a temperature up to 500° C. at a temperature-elevating speed of 10° C./min or less under pressure of 10 -1  Torr or less for 30 minutes or more to remove said mineral oil and/or said synthetic oil from said green body; and then sintering said green body.